I dont think this is supported to connect / control via the USB, as far, as i am aware, someone correct me on this if i am wrong please...
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The only option right now is to control it via Ethernet. Ethernet on its own ( also Network access as such) isnt the same thing as it beeing connected to the Internet itself. You can build yourself an Stand-Alone Ethernet Network completely isolated from the Internet, if you want /need to, by simply connecting some kind of router / Ethernet Switch to the Camera via an Ethernet Cord and The Router / Switch to an Computer. As long as Computer and The Switch / Router isnt connected to the Internet (Wifi for example), your data will never get into contact with The Internet. For this kind of usecase i would use the most Basic Gigabit Ethernet Switch and A PC without Wifi alltogether, if i wanted to be sure.